Ladder warning device

ABSTRACT

A warning device involving a rigid section of ladder is pivotally suspended from a tank, tower, building or the like and adapted to move slightly upon an intruder placing weight upon the section of ladder. Means are provided for biasing the ladder section in one direction, with the arrangement being such that upon an intruder placing weight upon the ladder, it overcomes this bias and actuates a warning device. The warning device may take the form of a switch which, when actuated, operates an alarm at a remote location, thus alerting a guard or the police of the trespass by the intruder. Significantly, all aspects of this device are inconspicuous, the motion of the ladder is slight, and the intruder in almost all instances will be unaware of the fact that his presence has been detected. Also, the arrangement resets itself automatically, and cannot be actuated by an accumulation of snow and ice.

United States Patent (151 3, 96,372 Garrett, deceased et al. 51 Oct. 3,1972 1 LADDER WARNING DEVICE FOREIGN PATEN'IS 0R APPLICATIONS 1Inventors: Leo Lawrence Gm 529,511 12/1940 Great Britain ..340/272Orlando, Fla; The Florida National Bank at Orlando, administrator, PO.Box 3593, Orlando, Fla. 33112; Walter L. Birdyshaw, Box 301 Bay St.,Ocoee, Fla. 32761 [22] Filed: Sept. 21, 1970 [21] Appl. No.2 74,113

Related US. Application Data [63] Continuation of Ser. No. 679,297, Oct.27,

1967, abandoned.

[52] US. Cl. ..340/272, 182/18, 200/85 [51 Int. Cl. ..E06c 5/34, G08b13/02 [58] Field of Search ..340/272; 200/86, 85, 61.58; 182/18 [56]References Cited UNITED STATES PATENTS 3,012,633 12/1961 Magee ..182/18X3,298,012 1/1967 Weller ..340/272 849,651 4/1907 Ashford ..340/2723,295,833 1/1967 Everett ..340/272 X Primary Examiner-John W. CaldwellAssistant Examiner-Scott F. Partridge ABSTRACT A warning deviceinvolving a rigid section of ladder is pivotally suspended from a tank,tower, building or the like and adapted to move slightly upon anintruder placing weight upon the section of ladder. Means are providedfor biasing the ladder section in one direction, with the arrangementbeing such that upon an intruder placing weight upon the ladder, itovercomes this bias and actuates a warning device. The warning devicemay take the form of a switch which, when actuated, operates an alarm ata remote location, thus alerting a guard or the police of the trespassby the intruder. Significantly, all aspects of this device areinconspicuous, the motion of the ladder is slight, and the intruder inalmost all instances will be unaware of the fact that his presence hasbeen detected. Also, the arrangement resets itself automatically, andcannot be actuated by an accumulation of snow and ice.

13 Claims, 5 Drawing Flgures PATENTEDum I972 SHEET 1 0F 4 INVENTORS LeoL. Garrett Walter L. Birdyshaw By z PATENTED U 3 I972 SHEEI 2 [IF 4mvzurozzs Leo L. Garrett Walter L.Birdyshaw PATENTEU 0m 3 I972 SHEET u[1F 4 INVENTORS LE 0 L.GARRETT n w m H O s w W A W Q I R E U A W LADDERWARNING DEVICE This application is a continuation of application679,297, filed Oct. 27, 1967 and now abandoned.

This invention relates to a warning device adapted to prevent anintruder from climbing undetected upon a tank, tower, building or othertype structure using a ladder or stair, and more particularly to animproved type of a ladder warning device in which a length or section ofthe ladder or stair on the side of such tank or structure is pivotallysuspended in such a manner that it can move slightly to inconspicuouslyreveal the presence of an intruder, yet automatically reset itself forfuture operation subsequent to the removal of weight therefrom.

Ever since the turn of the century, various intruder detectors have beenproposed for use with ladders or stairs, but these have been rudimentarytype devices in which the intruder often became aware of the betrayal ofhis presence, not only by virtue of detectable movement of the stair orladder, but also in many instances an alarm was sounded that was asaudible to him as it was to the owner of the property.

A comparatively recently issued patent proposes a Ladder Warning Devicefor use with tall towers or the like, but it utilizes a slidable laddersection suspended by the use of springs and chains at a mid-portion ofthe ladder. That slidable section can move to reveal the presence of theintruder, and although that patentee asserts that the suspensionarrangement could be made inconspicuous, it more likely than not couldbe sensed by the average prudent person, who might easily be able todisable the system. Furthermore, the slidable ladder section might wellbecome loaded down with snow and ice or mud, thus causing a warningsignal to be sent continuously, even though no unauthorized person werein the vicinity.

In contrast, the present invention provides in accordance with itsprincipal embodiment, a pivotally suspended section of ladder severalrungs or steps in length, which is arranged to move only very slightlyat its lower portion in the event that an intruder places weight uponit. Because this arrangement comprehends a section of ladder of sturdyconstruction, suspended from comparatively massive pivot points disposedadjacent the uppermost portion of this novel ladder section, ourinvention is not susceptible to being actuated by a load of ice and snowor mud. Also, the motion detection arrangement used with this inventionis quite inconspicuous, and only an intruder familiar with the systemcould detect the warning arrangement because of the unobviousconstruction of all components used therewith.

In this preferred embodiment, the base of the pivotal section of ladderis spring-biased away from the supporting structure of the tank orbuilding, with the movement of the section toward the structure anextent of only A: of an inch or so being sufficient to set off an alarmin a remote location, which of course enables the guards or the policeto apprehend the intruder in the act.

Another embodiment of our invention is designed for use with the curvedtype of ladder that may be used around the central column of a tank,such as a water tank, with a section of several steps or rungs of suchladder being pivotally supported at its upper end so that the movementof the lower end can take place to a sufficient extent to warn of thepresence of an intruder.

It is therefore a principal object of our invention to provide a lowcost yet effective ladder warning device that is extremely difficult forthe intruder to detect, which cannot be disabled by snow and ice or mud,and which resets itself automatically in a highly dependable mannerdespite many years of use.

These and other objects, features, and advantages will be more apparentfrom a study of the enclosed drawings in which:

FIG. 1 is a perspective view of the leg of a tank or the like, showing asection of ladder in accordance with one embodiment of this invention;

FIG. 2 is an enlarged perspective view of our invention, with certainportions removed, in which details of the suspension, motion detectionmeans, and spring bias arrangements are revealed;

FIG. 3 illustrates a first embodiment of a curved stair arrangement,such as may be used in connection with the circular stairway about thecentral pipe of a large tank; and

FIG. 3a illustrates a connecting mechanism for securing the steps ofFIG. 3.

FIG. 4 is another curved stair embodiment.

Referring now to FIG. I, it will be noted that the structural leg 10 ofa water tank or the like is provided with a comparatively rigid sectionof ladder 11 in accordance with our invention, in which comparativelymassive pivotal support members 12 are provided at the top of the laddersection to support it effectively at all times. Because these supportmembers 12 are in the form of pivots, the bottom end of the ladder cammove slightly toward the leg 10 so as to give a warning signal at suchtime as an intruder places weight on one or more rungs 13 of the ladder,with no restraint to this motion being provided by the pivotal supports.As will be seen hereinafter, the bottom portion of the ladder is biasedslightly away from the position in which a warning signal is given, sothat only at such time as an intruder places his weight and utilizesclimbing action on this section of the ladder will the bias be overcome,and the ladder move so as to cause a signal to be sent to the desiredremote location.

As will be noted from this figure, the movable section of ladder maycomprise only a fraction of the overall length of the ladder, and suchsection can be disposed at any of a variety of locations in a givenladder arrangement so as to make detection of its presence unlikely. Inthe present instance, the movable ladder portion is below fixed portion14. By virtue of the fact that the comparatively movable section ofladder involves a number of rungs, it will be difficult, if notimpossible, for the intruder to circumvent the section, even though hesuspected the utilization of an intruder warning device.

The sturdy design of the pivotal support members and other components ofour ladder warning arrangement is such that even an accumulation of snowand ice thereon will not interfere with proper operation. Also,

Referring to FIG. 2, it will be noted that the pivotal support means 12includes in addition to a pair of bolts, a pair of plates 12a welded orotherwise secured to the tank leg 10. The lower end of the fixed upperladder section 14 may also be secured to these plates.

At the lower end of the comparatively movable ladder section 11, plates18 are secured such as by welding, these plates ordinarily beingutilized in pairs. These plates 18 are preferably disposed so as toslightly overlap a pair of plates 19 that are welded or otherwisesecured to leg 10, with the arrangement being such that as an intruderplaces weight on one or more of the rungs 13 of the ladder section 1 l,the plates 18 move so as to overlap the plates 19 to a greater extent.This relative motion is utilized in accordance with this embodiment ofour invention to actuate the motion detection means now about to bedescribed.

A switch unit 16, utilizing a micro-switch or a mercury switch, ismounted upon plate 19, such switch preferably being in a water-tightenclosure of the type shown. Extending outwardly from the switch unit 16is a push rod 17, which is movable into and out of the switch unit. Theend of the push rod remote from the switch unit is secured to plate 18,so as therefore will be understood, motion of the plate 18 toward theswitch unit 16 as a result of climbing action on the movable section ofladder will bring about actuation of the switch, with preferably analarm or warning light being actuated at a remote location. Damage tothe switch as a result of too much motion can be prevented by the use ofa stud and slot arrangement 22 utilized in the overlap portion of plates18 and 19. A typical amount of motion permitted by this arrangement is Ainch, which is usually ample for proper switch operation.

In order to provide a positive resetting of the switch subsequent to theremoval of weight from the movable section of ladder, we provide inaccordance with this invention a bias in the form of a pair of springunits 21 whose bases are secured to the plates 19, and whose outerportions may be secured to the movable ladder portion 11. These springsserve to bias the movable ladder section to a sufficient extent aboutthe pivotal support members that resetting of the switch 16 is assured.Adjustment means are provided so that the desired weight required tooperate the ladder warning system can be preset. These springs arepreferable enclosed in a weather-proof cover.

As will be apparent, upon an intruder placing weight upon the movableladder section 11, the springs 21 are compressed to a sufficient extentthat the push rod 17 will actuate the switch 16, and thus bring about awarning Signal being given. For example, the switch 16 can be wired intoa circuit arranged to provide a signal at either a local or a remotelocation, such as operating a light and/or warning bell on a switchboard or control panel at a guard station. Such signal could betransmitted either by the use of wires or radio signals. Referring to FIG. 3, it will be noted that a fixed step 26 and a fixed railing 31characterize the type of circular staircase utilized around the centralcolumn of one type of tank. Several movable steps 27 which togetherconstitute a movable ladder section are also shown in this figure, witheach of the moveable rungs or steps being suspended at their outer endsby means of rods 30 from a movable bannister or railing 33. The railing33 is pivotally connected at 32 to the fixed portion 31 of the railing,with pivot 32 serving as a pivotal support means for this movable laddersection.

The inner portion 28 of each of the movable rungs or steps is secured tothe central section 36 of the tank, with a connecting pin 29 or the likebeing utilized for securing the step portions 27 and 28 together in aproper manner; see FIG. 3a.

The lowermost movable step forms some support for the lower portion ofthe movable section of ladder in accordance with this embodiment,inasmuch as the outer end of the step is provided with a pair ofcompression springs 34 which serve to bias the outer end of the lowerstep, which unit is provided with a push rod 37 in contact with theunderside of the step.

As will be apparent, upon an intruder placing weight on any part of themovable ladder section in accordance with this embodiment, the springs34 are.

compressed to a sufficient extent that the push rod 37 will be moveddownwardly to bring about actuation of the switch 35, and thus actuate awarning arrangement. For example, the switch 35 can be wired into acircuit arranged to provide a signal at a remote or local location, suchas lighting a light and/or operating a warning bell or siren at theguard station or maintenance office. Such signal can be transmittedeither by the use of wires or radio signals.

The design of the transmission device can vary as desired, for either atelephone system, a private wire, or radio system can be used forcarrying the signal to a remote location. The switches are designed sothat they can be installed in standard electrical fittings which willmake it virtually impossible for an intruder to determine that an alarmsystem has been installed.

Turning now to FIG. 4, a curved ladder embodiment generally resemblingthe embodiment in accordance with FIG. 3 is illustrated, in which amodified form of pivotal support means is disposed adjacent a rigidladder section. This section comprises steps or rungs 47, 48 and 49,with the outer ends of these three steps being supported by means ofvertical bars 40 from a railing 43 that in turn is pivotally attached at42 to the fixed railing 41.

The inner ends of steps 47 through 49 are maintained in the desiredspaced relation by means of a bar 51 secured to each of these steps,with the upper end of this bar being pivotally supported at 52 from alug or bolt extending outwardly from central section 46 of the tank.Short members 53 extend between the inner front edges of steps or rungs48 and 49 and the bar 51, and the outer front edges of these steps arewelded or otherwise secured to respective bars 40, thus keeping thefront edges of these steps from tending to deflect undesirably.

A plurality of springs 44 are disposed beneath lowermost step 47,tending to bias this three-step section of ladder in one direction aboutpivot means 42 and 52, but of course this bias is overcome at such timeas an intruder places weight upon any of these three steps. The railing43 and bar 51 serve to hold these steps in a unit or section, whichsection can pivot about its pivot points upon weight being placed atvirtually any location of the unit. Switch unit 45 is disposed adjacentor below step 47, which unit is caused to be actuated upon the springs44 being compressed a small amount. The

operating of the switch unit of course is arranged as in the otherembodiments to cause a signal to be given at a remote location.

As will now be apparent, we have provided an effective warning devicefor preventing an intruder from climbing undetected upon a ladder or thelike that is utilized on a tank or building. In each embodiment, pivotalsupport means are disposed adjacent an upper end of a movable section ofladder, with bias means being used to bias the section of ladder in agiven direction about the pivotal support means. The section of laddertends to pivot about the pivotal support means in a direction oppositesaid given direction upon weight being placed upon said section ofladder, and motion detection means are disposed in cooperative relationwith said section of ladder, to sense motion about said pivotal supportmeans resulting from the placement of weight upon said section.Advantageously, the motion detection means resets itself automaticallyafter the removal of weight from said section of ladder, with the resultthat little if any maintenance is necessary.

A cover is preferably provided over the switch unit and push rodassembly of FIG. 2, as indicated by the broken lines, this not onlypreventing an accumulation of dirt or snow, but also serving to renderthis assembly even more inconspicuous than it would otherwise be. Theswitch units of the other embodiments may likewise be provided with acover, although the disposition of a switch unit below the lowermoststep makes its detection highly unlikely.

It is claimed:

1. A warning device for preventing an intruder from climbing undetectedupon a ladder comprising a comparatively rigid section of ladderequipped with a plurality of rungs and having an upper end and a lowerend, stationary support means disposed adjacent the upper end of saidsection of ladder, for forming the principal support for said section ofladder, the upper end of said section of ladder being directly andpivotally attached to said support means for rotational deflection to aslight extent under the weight of a person stepping on the rungs, butnot downward deflection, thus minimizing the extent of ladder travel andthe conspicuousness of the motion, means biasing said section of ladderin a given direction about said pivotal support means, said section ofladder tending to pivot about said support means in a direction oppositesaid given direction upon weight being placed upon said section ofladder, and motion detection means disposed in cooperative relation withsaid section of ladder to sense the slight motion about said supportmeans resulting from the placement of weight upon said section ofladder.

2. The warning device as defined in claim 1 in which said motiondetection means resets itself automatically after the removal of weightfrom said section of ladder.

3. The warning device as defined in claim 1 in which said comparativelyrigid section of ladder is substantially straight.

4. The warning device as defined in claim 1 in which said comparativelyrigid section of ladder forms at least a portion of circular staircase.

5. The warning device as defined in claim 1 in which said motiondetection means is arranged to actuate an alarm in a remot locati n.

. A warning evice or preventing an intruder from climbing undetectedupon a ladder, said ladder comprising a comparatively fixed section,adjacent which a comparatively movable section is supported as acontinuation thereof, said comparatively movable section being rigid andhaving a plurality of rungs, and having an upper end and a lower end,stationary support means disposed adjacent the upper end of saidcomparatively movable section of ladder, for forming the principalsupport for latter section of ladder, said upper end of saidcomparatively movable section of ladder being pivotally attached to saidsupport means such that said upper end can deflect rotationally to aslight extent under the weight of a person stepping on the rungs but notdownwardly, thus minimizing the extent of ladder travel and theconspicuousness of the motion, means biasing said movable ladder sectionin a first direction about said pivotal support means, said movableladder section being movable in a direction opposite said firstdirection as a result of the weight of an intruder thereon, and motiondetection means arranged to be actuated at such time as said movableladder section is moved in a direction opposite said first direction,whereby an alarm may be given.

7. The warning device as defined in claim 6 in which said motiondetection means resets itself automatically after the removal of weightfrom said movable section of ladder.

8. The warning device as defined in claim 6 in which said fixed andmovable ladder sections are substantially straight sections, disposed ata comparatively steep angle against a structure.

9. The warning device as defined in claim 6 in which said fixed andmovable ladder sections together form at least a portion of a curvedladder.

10. The warning device as defined in claim 6 in which said motiondetection means is arranged to actuate an alarm in a remote location.

11. A warning device for preventing an intruder from climbing undetectedupon a ladder comprising a comparatively rigid section of ladderequipped with a plurality of steps, stationary support means disposedadjacent an upper end of said section of ladder, for forming theprincipal support for said section of ladder, the upper end of saidsection of ladder being pivotally attached to said support means, suchthat said upper end can deflect rotationally to a slight extent underthe weight of a person stepping on the steps, but not downwardly, thusminimizing the extent of ladder travel and the conspicuousness of themotion, said sec tion of ladder tending to pivot slightly about saidsupport means upon weight being placed upon said section of ladder, andmotion detection means disposed in cooperative relation with saidsection of ladder, to sense motion about said support means resultingfrom the placement of weight upon said section of ladder, and to give analarm at a remote location.

12. The warning device as defined in claim 11 in which saidcomparatively rigid section of ladder is substantially verticallydisposed.

13. The warning device as defined in claim 11 in which saidcomparatively rigid section of ladder forms at least a portion of acircular staircase.

1. A warning device for preventing an intruder from climbing undetectedupon a ladder comprising a comparatively rigid section of ladderequipped with a plurality of rungs and having an upper end and a lowerend, stationary support means disposed adjacent the upper end of saidsection of ladder, for forming the principal support for said section ofladder, the upper end of said section of ladder being directly andpivotally attached to said support means for rotational deflection to aslight extent under the weight of a person stepping on the rungs, butnot downward deflection, thus minimizing the extent of ladder travel andthe conspicuousness of the motion, means biasing said section of ladderin a given direction about said pivotal support means, said section ofladder tending to pivot about said support means in a direction oppositesaid given direction upon weight being placed upon said section ofladder, and motion detection means disposed in cooperative relation withsaid section of ladder to sense the slight motion about said supportmeans resulting from the placement of weight upon said section ofladder.
 2. The warning device as defined in claim 1 in which said motiondetection means resets itself automatically after the removal of weightfrom said section of ladder.
 3. The warning device as defined in claim 1in which said comparatively rigid section of ladder is substantiallystraight.
 4. The warning device as defined in claim 1 in which saidcomparatively rigid section of ladder forms at least a portion ofcircular staircase.
 5. The warning device as defined in claim 1 in whichsaid motion detection means is arranged to actuate an alarm in a remotelocation.
 6. A warning device for preventing an intruder from climbingundetected upon a ladder, said ladder comprising a comparatively fixedsection, adjacent which a comparatively movable section is supported asa continuation thereof, said comparatively movable section being rigidand having a plurality of rungs, and having an upper end and a lowerend, stationary support means disposed adjacent the upper end of saidcomparatively movable section of ladder, for forming the principalsupport for latter section of ladder, said upper end of saidcomparatively movable section of ladder being pivotally attached to saidsupport means such that said upper end can deflect rotationally to aslight extent under the weight of a person stepping on the rungs but notdownwardly, thus minimizing the extent of ladder travel and theconspicuousness of the motion, means biasing said movable ladder sectionin a first direction about said pivotal support means, said movableladder section being movable in a direction opposite said firstdirection as a result of the weight of an intruder thereon, and motiondetection means arranged to be actuated at such time as said movableladder section is moved in a direction opposite said first direction,whereby an alarm may be given.
 7. The warning device as defined in claim6 in which said motion detection means resets itself automatically afterthe removal of weight from said movable section of ladder.
 8. Thewarning device as defined in claim 6 in which said fixed and movableladder sections are substantially straight sections, disposed at acomparatively steep angle against a structure.
 9. The warning device asdefined in claim 6 in which said fixed and movable ladder sectioNstogether form at least a portion of a curved ladder.
 10. The warningdevice as defined in claim 6 in which said motion detection means isarranged to actuate an alarm in a remote location.
 11. A warning devicefor preventing an intruder from climbing undetected upon a laddercomprising a comparatively rigid section of ladder equipped with aplurality of steps, stationary support means disposed adjacent an upperend of said section of ladder, for forming the principal support forsaid section of ladder, the upper end of said section of ladder beingpivotally attached to said support means, such that said upper end candeflect rotationally to a slight extent under the weight of a personstepping on the steps, but not downwardly, thus minimizing the extent ofladder travel and the conspicuousness of the motion, said section ofladder tending to pivot slightly about said support means upon weightbeing placed upon said section of ladder, and motion detection meansdisposed in cooperative relation with said section of ladder, to sensemotion about said support means resulting from the placement of weightupon said section of ladder, and to give an alarm at a remote location.12. The warning device as defined in claim 11 in which saidcomparatively rigid section of ladder is substantially verticallydisposed.
 13. The warning device as defined in claim 11 in which saidcomparatively rigid section of ladder forms at least a portion of acircular staircase.